Powder mixtures having a cellulose ether binder are used in forming articles of various shapes. For example ceramic or metal powder mixtures are formed into honeycombs which are used as substrates in catalytic and adsorption applications. The mixtures must be well blended and homogeneous in order for the resulting shaped body to have good integrity in size and shape and uniform physical properties. The mixtures have organic additives in addition to the binders. These additives can be surfactants, lubricants, and dispersants and function as processing aids to enhance wetting thereby producing a uniform batch.
Rapid-setting characteristics are important for honeycomb substrates. If the cell walls of the honeycomb can be solidified quickly after forming, the dimension of the greenware will not be altered in subsequent cutting and handling steps. This is especially true for a fragile thin-walled or complex shaped product, or a product having a large frontal area.
In injection molding, a ceramic batch can be classified roughly into two categories: a non-aqueous batch with solvent, soluble binders, and additives; and an aqueous batch with water soluble or dispersible binders.
In general an aqueous batch is harder or slower to set up than a non-aqueous one. But a non-aqueous batch has the disadvantage of using solvent(s) which cause environmental problems and require costly facilities to process.
Up to this time it has always been accepted that an aqueous cellulose ether batch will not be compatible with any hydrophobic additive. The only practical way to introduce a substantial amount of hydrophobic material to an aqueous ceramic batch at low temperature (room temperature) is by an aqueous emulsion or dispersion of that material. Since no large temperature difference is involved in such addition, the unique melting/solidifying feature of a hydrophilic material cannot be realized in a ceramic batch. Moreover, there is always the question concerning the distribution and effectiveness of discrete hydrophobic particles in an aqueous environment.
It would be advantageous to improve the setting up characteristics of formable mixtures. It would be a distinct advantage from an environmental and cost standpoint to be able to use aqueous batches. Therefore a method to improve the setting up characteristics of aqueous batches so they would set up easier and faster would be highly desirable and an advancement in the art.